X-Phase-QRM-Eliminator

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Click HERE for the KC9ON build guide.

The kit was the standard Chinese style kit consisting of a “bag of parts” for $10. I had to hunt down a schematic and other assembly guides which helped but were not complete. Hence the writing of this guide.

Assembly itself went together well. The only issue I found was the tight area where the transformer is soldered on. After picking up the remained of the parts needed such as wires, connectors, enclosure, etc. I would say spend the extra money and get either a full kit or fully assembled unit. I probably spent more on the accessories than the PCB itself. Another assembly issue was the lack of an enclosure so designed a 3D printed one. I probably should have made the enclosure a bit deeper as the coax cables were a bit tight when placing the rear panel on. I also should have went with BNC or UHF connectors instead of the SMA but have been trying to use SMA for all my QRP/SDR equipment.

As far as operating – it takes a bit of fiddling to get it working correctly. Position and location of the sense antenna is also important. I found my neighbors solar panels emit some horrible noise in the daytime just above the 40M band on my end fed antenna. To pick up the noise I used my 40M dipole which is located farther away. Although it did reduce the noise I found swapping antennas did a slightly better job but that would limit my transmit to 40M. Could it be the sense antenna needs to be closer to the noise source??? Back to using the end fed as the main antenna I found the best noise reduction is to put the gain down to 0 on the main so appears the real signal is being picked up with the sense antenna and the main is helping remove the noise. Your mileage may vary! In this configuration I also noticed a reduction of real signal levels with some toward the noise floor disappearing. However, with this amount of noise the eliminator is still a good sacrifice.

I did not try the PTT for transmit at this time as using an RTL-SDR dongle to see the noise.

Below are a couple screen shots showing the eliminator in progress.

 

40&41M Band Before

40&41M Band After

CHU 7.850MHz Before

CHU 7.850MHz After

 

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